(1) Field of the Invention
The present invention relates to a honing head for honing the internal cylindrical surface of a bore in a workpiece, and more particularly to a honing head capable of honing a workpiece at high speeds for high-performance honing operation.
(2) Prior Art
The internal cylindrical surface of a hole in a workpiece can be honed by rotating and reciprocating a honing head in the hole to enable honing stones mounted on the head to finish the cylindrical surface to a high degree of accuracy. Conventional honing heads rotate at speeds lower than those at which boring and other machines operate. Known honing heads generally comprise a hollow holder serving as a head body and having a plurality of radial guide slots defined therethrough and spaced at equal intervals from each other in the circumferential direction, a cone shaft axially reciprocably disposed in the holder, and a plurality of honing stone supports radially movably received in the guide slots, respectively, each of the honing stone supports having at least one radially inward cam surface held against at least one radially outward tapered surface defined on the cone shaft and extending axially thereof. When the cone shaft moves axially forwardly or rearwardly, the honing stone supports expand radially outwardly as they are guided by the guide holes to hold honing stones mounted on the honing stone supports against the cylindrical wall to be finished. The honing head is adapted to float in the hole in the workpiece by a universal joint. The head is caused to rotate and at the same time reciprocable as the honing stones slide along the hole surface to effect a low-speed honing operation. To prevent the honing stone supports from being forced out due to centrifugal forces and to retract them radially inwardly after the honing operation is finished, a common angular resilient member such as a spring is mounted on radially outward surfaces of the honing stone supports to fasten the supports together.
To carry out such a honing process at higher speeds for high-performance honing operation, it would be preferable to dispense with the universal joint and provide a sleeve member rearwardly of the honing head to receive the latter therein for reciprocating movement. The honing head would be provided therearound with boring tools such as cutting tools so as to be able to effect both boring operation and subsequent honing operation. With such an arrangement, a single machine can be used for different kinds of machining operations, workpieces can be machined in a shorter period of time, and machining operations can be performed with improved efficiency.
For such a high-speed honing operation, however, it is not desirable to rely on the prior honing head constructed as described above, and there has thus developed a desideratum for a novel honing head which meets the requirements of high-speed honing processes. More specifically, the structure wherein the honing stone supports are fastened radially inwardly by the annular resilient member to protect against centrifugal forces acting on the supports or to retract the supports radially inwardly cannot be put to practical use. A desired honing head should be constructed such that it will keep honing stone supports in position reliably against centrifugal forces due to high-speed rotation, and the honing stone supports can forcibly be withdrawn into the head after the honing operation is completed. The body of such a honing head should have an increased degree of mechanical strength and rigidity because insufficient rigidity of the head body tends to render the honing stone supports unstable during honing operation. Especially where the honing head is provided with boring tools for performing boring operations, the boring tools are liable to be vibrated when subjected to increased stresses during the boring operation, resulting in less accuracy of bored surfaces.